DOUBLE NEEDLE CHAIN STITCH
STITCH CLASS 400 : MULTI THREAD CHAIN STITCH This stitch type is formed by inter-looping of two or more groups of thread. Stitch formation in the stitch type 401
MACHINE COMPONENTS • Thread tension mechanism • Thread tension Nut • Tension post holder • Thread Eye-let ( 5 nos. ) • Thread take-up plate • Needle Thread Guard • Needle bar and lever Mechanism • Needle lever • Needle Bar guide and clamp • Ball joint
Feed Mechanism • Feed-dog • Feed rocker arm • Rear puller • Feed-dog slots • Looper Mechanism • Looper • Looper Rocker • Take-up Rod • Looper Holder Bracket
Presser Foot Mechanism • Presser Bar • Presser Screw • Lifter Lever Spring • Presser Foot Lifter Lever • Presser Bar Guide • Presser Bar Spring
NEEDLES Schmetz- UY113GS Organ – UO113GS Groz-beckert- TVx64 Needles and needle sizes
THREADING Threading of the machine is very important • Incorrect threading may cause: • Skip stitch • Thread breakage • Uneven stitch formation
MACHINE SPEED Chain stitch machine can have a speed up to 8000rpm
FEED MECHANISM • Unison Feed Mechanism: • It is a combination of three feed mechanisms • Conventional feed mechanism • Needle feed mechanism • Alternating presser foot
TIMING OF THE LOOPER TO NEEDLES Angle for installing the looper and position of the looper holder bracket There should be a clearance of 0~0.1mm between the point of the looper and the scarf of the needle
ADJUSTING THE TIMING OF THE RETAINER LOOPER Position of the retainer loop There should be a clearance of 0.5mm between the needle and the point of the retainer looper. Adjustment is made by loosening b as shown in the fig.
Timing of the retainer looper to the needle When the needle, moving from top to bottom of Its stroke, enters the triangle of the looper thread, the retainer Looper should be at the extreme right end of its travel The clearance between the retainer looper and the right side of looper should we 0.5 mm. The clearance between the retainer looper and the top surface of the looper blade at 0.1mm
ADJUSTING THE NEEDLE GUARD Position of the needle guard When the needle is closest to needle guard, there should be clearance of 0~0.1mm between the right side of the needle and the guard.
ADJUSTING THE FEED DOG & STITCH LENGTH When needle bar is at top of its stroke, the feed dog teeth should be 1~1.2mm above the top surface of the needle plate. Stitch length The stitch length can be adjusted from 2 to 5 mm.
ADJUSTING THE PRESSER FOOT Presser foot pressure should be as light as possible yet, sufficient to feed the fabric. Position of the presser foot Accurate placement so that the needle can drop correctly to the centre of the needle drop hole on the presser foot
ADJUSTING THE STITCH FORMATION Thread tension adjustment It can be adjusted by adjusting the mount tension devices on the machine ( The tension should be as light as possible ). Position of the needle thread eyelets Secure needle thread eyelets should be at the top end of the slot. ( The needle thread eyelets can be raised to tighten the needle thread )
APPLICATION OF DNCS • Inseam of jeans, trousers • In Jackets seams • Sewing sides of slacks • Hemming or welting garment parts • Attaching lining tapes • Joining seat of slacks
VARIATIONS IN DNCS • Variations in bed type • Cylindrical bed- feed of the arm • Raised bed • Flat bed • Variations in number of needles • 2 needle double needle chain stitch machine • 4 needle double needle chain stitch machine • 12 needle double needle chain stitch machine • 33 needle double needle chain stitch machine